The position of the sliding blocks on the movable crosspieces with respect to the sliding surfaces on the columns of the press may be adjusted during assembly and must be such that it is centred with respect to the movable crosspiece, and in the case of extruding presses also the container-holder crosspiece, with respect to the axis of the press in relation to wear of the sliding blocks and, in the case of a forging press, also in relation to thermal expansions of the movable crosspiece, which is subject to continuous exposure to radiation by the hot worked material during the work shift.
In the prior art, there is a first adjustment procedure based on measurements of the position of the crosspiece (on measurements of the clearance at different positions of the crosspiece in the case of die forging presses), on a theoretical calculation and on the experience of the operating personnel. Such adjustment may be then fine-tuned during the operation of the machine, also due to the wear of the sliding surfaces. The fine-tuning of the adjustment is usually performed occasionally and manually using adjustment screws or wedges and simple shim packages.
In the case of die forging presses, for a good mechanical stability of the press and for an optimal wear of the sliding blocks, it is advantageous to maintain limited clearances. However, for example in the case of die forging presses working in operating conditions of severe and prolonged exposure to radiations, the expansion of the movable crosspiece may be such as to close clearances conventionally acceptable in cold operation, with a subsequent dragging of the sliding blocks thus increasing the wear thereof, up to the locking of the rising movement of the crosspiece itself. Vice versa, in the case of extruding presses, the working hours involve an increasing wear of the sliding blocks, in particular of the lower sliding blocks, determining a lowering of the movable crosspiece and of the container holder crosspiece, sliding horizontally, and therefore a position of said crosspieces no longer centred to the horizontal longitudinal axis of the press. This implies a deterioration of the alignment of the press and a non-optimal quality of the extruded product.
Document JP2011152553 describes a press in which the adjustment of the sliding blocks takes place by means of a wedge moved vertically by an eccentric system. Disadvantageously such solution is bulky and expensive, providing for two parts separate relative to each other of the adjustment system to respectively perform, by means of two separate hydraulic cylinders, the adjustment function of the clearance by means of the eccentric system which shifts the wedge and the locking function of the wedge itself. Furthermore, such adjustment system is arranged inside the movable crosspiece, making this system more complex and difficult to access. The eccentric pin which allows adjusting the position of the movable wedge with respect to the fixed wedge, integral to the movable crosspiece, also passes through said fixed wedge, whereby numerous mechanical processes are needed to implement this technical solution.
The need of providing an adjustment system that allows the above drawbacks to be overcome is therefore felt.